From where I stand

Bacteria Tell an Interesting Story

Who knew that bacteria are social “creatures”? Yes, social! It turns out they do not act as separate organisms, but as communal organisms. Dr. Bonnie Brassler gives an interesting TED Talk on bacteria that explains what incredible social or communal organisms bacteria are, and these bacteria tell an interesting story.

Bacteria not only interact with themselves; they work in harmony with other more complex organisms. Bonnie Brassler points to the example of a squid that engages in an intricate dance with bacteria (virio fisheri) to provide an “ingenuous” anti-predator scheme that prevents the squid from casting a shadow. The symbiosis between the squid and bacteria is amazing, down to signal proteins given off by the squid and signal receptor proteins from the bacteria that are like “lock and key”.

It turns out this is no anomaly. All bacteria have systems like the bacterial friends of squid. “All bacteria can talk to each other. They make chemical words. They recognize those words, and they turn on group behaviors that are only successful when all of the cells participate in unison,” says Dr. Brassler. Scientists call this “quorum-sensing”.

Quorum sensing works like a bacterial group vote followed by bacterial group action in response to the vote. Dr. Brassler says that we now know of hundreds of group bacterial behaviors that are carried out in this collective fashion. One that is important to humans is virulence.

People are full of bacteria, most of which are beneficial bacteria that have a symbiotic relationship with us. In fact, the number of bacteria hosted in our bodies is astonishing high. Virulence occurs as the result of the collective behavior of “bad” bacteria. These bad bacteria have the ability to destroy their hosts if they accumulate in sufficient numbers.

These bacteria collect in people, but people are far bigger than anything that these bacteria can affect unless there are sufficient numbers of them. The bad bacteria collect until they have sufficient number, and then they launch themselves when they sense they have an advantage to overcome the host (our bodies).

It turns out, also, that bacteria molecules are related to each other. All bacteria molecules have certain characteristics that are identical in every bacteria, and each species of bacteria also have characteristics that are unique to the species. This allows different bacteria to have species specific language that involve “private, secret conversations”, according to Brassler. In this way, they can “count their own siblings”.

Bacteria, however, do not live only among themselves; they live among hundreds of thousands of other types of bacteria and other organisms. Thus, communicating among their own kind is not enough; they need to be able to communicate inter-species. Molecular biology has revealed, in fact, that bacteria are “multilingual”.

All bacteria have species specific characteristics and species specific systems, but they also have generic characteristics and systems that they share with other bacteria species. They have a second amino protein signal that is the “trade language” of all bacteria. In this way, bacteria can count how many of their own and how many not of their own exist in their environment, and they can process the information to determine collectively what tasks they will carry out depending on whether they are in the minority or majority in a given population.

The trade language molecule is a small, five-carbon molecule, and every single bacteria species has the same enzyme and makes exactly the same molecule. They all use the same molecule for inter-species communication.

What this means for scientists who are trying to find ways to fight bad bacteria is that these communication systems can be targeted. Simply put, an antibiotic that prevents the bacteria from counting and talking to each other may prevent them from “quorum-sensing” and, therefore, from being able to act together to attack their hosts (us!).

This is where the next generation of bacterial medicines are going. These medicines will involve species specific (disease specific) anti-quorum sensing molecules that are made to mimic the enzymes that lock into the bacteria receptors, and these man-made impostors will jam them. These medicines may include pro-quorum-sensing agents that will aid the beneficial bacteria in joining together to rise up to defeat the bad bacteria.

The implications of all of this, however, go well beyond bacteria, medicine and science. The complexity of life is truly remarkable. Bacteria are some of the oldest and “simplest” organisms on earth; yet we are learning that they behave in concert with each other! They “talk” to each other! They even appear to make group “decisions” on the basis of the information that they collectively evaluate!

What cause or mechanism in the natural world is sufficient to create this level of interrelationship and complexity? Even at the lowest forms of life, there is incredible complexity in the interaction and interrelationship with each other and with higher forms of life. How much faith must we put in random, unguided processes to believe they can create such complexity?

As for me, I do not have that much faith. The evidence I see of causes that use information, communication and interrelationship in this way point to one thing – that is intelligence or mind. Intelligence is the only known agent or cause of this kind of interrelated complexity. I can think of no other agent or cause without making something up (and minds are good at that too!).

Language (information ordered in functional, communicative ways) is what we see in the way bacteria behave and interact. We see language at the foundation of life, in our very DNA and the DNA of all living organisms. This language does not suggest that bacteria are intelligent; it does not suggest that all life forms are intelligent; but it suggests there is intelligence behind life.

Postscript:

Though I have briefly described the gist of the TED Talk, I recommend watching Dr. Bonnie Brassler, herself, explain the world of bacteria in more detail and with much more enthusiasm than I could muster for our bacterial friends.